1// SPDX-License-Identifier: GPL-2.0
  2// LPC variant I/O for Microchip EC
  3//
  4// Copyright (C) 2016 Google, Inc
  5
  6#include <linux/delay.h>
  7#include <linux/io.h>
  8#include <linux/mutex.h>
  9#include <linux/types.h>
 10
 11#include "cros_ec_lpc_mec.h"
 12
 13/*
 14 * This mutex must be held while accessing the EMI unit. We can't rely on the
 15 * EC mutex because memmap data may be accessed without it being held.
 16 */
 17static DEFINE_MUTEX(io_mutex);
 18static u16 mec_emi_base, mec_emi_end;
 19
 20/**
 21 * cros_ec_lpc_mec_emi_write_address() - Initialize EMI at a given address.
 22 *
 23 * @addr: Starting read / write address
 24 * @access_type: Type of access, typically 32-bit auto-increment
 25 */
 26static void cros_ec_lpc_mec_emi_write_address(u16 addr,
 27			enum cros_ec_lpc_mec_emi_access_mode access_type)
 28{
 29	outb((addr & 0xfc) | access_type, MEC_EMI_EC_ADDRESS_B0(mec_emi_base));
 30	outb((addr >> 8) & 0x7f, MEC_EMI_EC_ADDRESS_B1(mec_emi_base));
 31}
 32
 33/**
 34 * cros_ec_lpc_mec_in_range() - Determine if addresses are in MEC EMI range.
 35 *
 36 * @offset: Address offset
 37 * @length: Number of bytes to check
 38 *
 39 * Return: 1 if in range, 0 if not, and -EINVAL on failure
 40 *         such as the mec range not being initialized
 41 */
 42int cros_ec_lpc_mec_in_range(unsigned int offset, unsigned int length)
 43{
 44	if (length == 0)
 45		return -EINVAL;
 46
 47	if (WARN_ON(mec_emi_base == 0 || mec_emi_end == 0))
 48		return -EINVAL;
 49
 50	if (offset >= mec_emi_base && offset < mec_emi_end) {
 51		if (WARN_ON(offset + length - 1 >= mec_emi_end))
 52			return -EINVAL;
 53		return 1;
 54	}
 55
 56	if (WARN_ON(offset + length > mec_emi_base && offset < mec_emi_end))
 57		return -EINVAL;
 58
 59	return 0;
 60}
 61
 62/**
 63 * cros_ec_lpc_io_bytes_mec() - Read / write bytes to MEC EMI port.
 64 *
 65 * @io_type: MEC_IO_READ or MEC_IO_WRITE, depending on request
 66 * @offset:  Base read / write address
 67 * @length:  Number of bytes to read / write
 68 * @buf:     Destination / source buffer
 69 *
 70 * Return: 8-bit checksum of all bytes read / written
 71 */
 72u8 cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
 73			    unsigned int offset, unsigned int length,
 74			    u8 *buf)
 75{
 76	int i = 0;
 77	int io_addr;
 78	u8 sum = 0;
 79	enum cros_ec_lpc_mec_emi_access_mode access, new_access;
 80
 81	/* Return checksum of 0 if window is not initialized */
 82	WARN_ON(mec_emi_base == 0 || mec_emi_end == 0);
 83	if (mec_emi_base == 0 || mec_emi_end == 0)
 84		return 0;
 85
 86	/*
 87	 * Long access cannot be used on misaligned data since reading B0 loads
 88	 * the data register and writing B3 flushes.
 89	 */
 90	if (offset & 0x3 || length < 4)
 91		access = ACCESS_TYPE_BYTE;
 92	else
 93		access = ACCESS_TYPE_LONG_AUTO_INCREMENT;
 94
 95	mutex_lock(&io_mutex);
 96
 97	/* Initialize I/O at desired address */
 98	cros_ec_lpc_mec_emi_write_address(offset, access);
 99
100	/* Skip bytes in case of misaligned offset */
101	io_addr = MEC_EMI_EC_DATA_B0(mec_emi_base) + (offset & 0x3);
102	while (i < length) {
103		while (io_addr <= MEC_EMI_EC_DATA_B3(mec_emi_base)) {
104			if (io_type == MEC_IO_READ)
105				buf[i] = inb(io_addr++);
106			else
107				outb(buf[i], io_addr++);
108
109			sum += buf[i++];
110			offset++;
111
112			/* Extra bounds check in case of misaligned length */
113			if (i == length)
114				goto done;
115		}
116
117		/*
118		 * Use long auto-increment access except for misaligned write,
119		 * since writing B3 triggers the flush.
120		 */
121		if (length - i < 4 && io_type == MEC_IO_WRITE)
122			new_access = ACCESS_TYPE_BYTE;
123		else
124			new_access = ACCESS_TYPE_LONG_AUTO_INCREMENT;
125
126		if (new_access != access ||
127		    access != ACCESS_TYPE_LONG_AUTO_INCREMENT) {
128			access = new_access;
129			cros_ec_lpc_mec_emi_write_address(offset, access);
130		}
131
132		/* Access [B0, B3] on each loop pass */
133		io_addr = MEC_EMI_EC_DATA_B0(mec_emi_base);
134	}
135
136done:
137	mutex_unlock(&io_mutex);
138
139	return sum;
140}
141EXPORT_SYMBOL(cros_ec_lpc_io_bytes_mec);
142
143void cros_ec_lpc_mec_init(unsigned int base, unsigned int end)
144{
145	mec_emi_base = base;
146	mec_emi_end = end;
147}
148EXPORT_SYMBOL(cros_ec_lpc_mec_init);